Electric compressor for vehicle air conditioner

ABSTRACT

An electric compressor for a vehicle air conditioner capable of preventing refrigerant leakage is provided. A case ( 77 ) is formed by injecting a molten metal into a mold, and a compression unit for compressing a refrigerant is accommodated inside, wherein a machined portion ( 123 ) is formed on one of an inner circumferential surface ( 77 A) in contact with the refrigerant and an outer circumferential surface adjacent to the inner circumferential surface.

TECHNICAL FIELD

The present invention relates to an electric compressor for a vehicleair conditioner.

BACKGROUND ART

With conventional integrated-inverter electric compressors for vehicleair conditioners (electric compressors for vehicle air conditioners), amethod for driving a scroll compressor using a fixed scroll and anorbiting scroll with an electric motor is widely used (for example, seePatent Documents 1 to 7).

In the above-described electric compressor, an inverter case thataccommodates an inverter unit for supplying electrical power to theelectric motor and a pressure case that accommodates, for example, theelectric motor or a compression unit are integrally formed bydie-casting using, for example, aluminum as a material.

Many screw holes used for attaching an inverter unit are often formed inthe interior of such an inverter case.

Patent Document 1: Japanese Unexamined Patent Application, PublicationNo. 2007-162661

Patent Document 2: The Publication of Japanese Patent No. 3802477

Patent Document 3: The Publication of Japanese Patent No. 3843809

Patent Document 4: Japanese Unexamined Patent Application, PublicationNo. 2005-188441

Patent Document 5: Japanese Unexamined Patent Application, PublicationNo. 2007-128756

Patent Document 6: Japanese Unexamined Patent Application, PublicationNo. 2005-180292

DISCLOSURE OF INVENTION

As described above, when many screw holes are formed inside the invertercase, shrinkage cavities communicate between the screw holes and amachined surface, in the pressure case, facing the screw holes, andthus, refrigerant in the pressure case tends to leak outside through theshrinkage cavities.

The present invention has been conceived to solve the above-describedproblems, and an object thereof is to provide an electric compressor fora vehicle air conditioner capable of preventing refrigerant leakage.

To realize the object described above, the present invention providesthe following solutions.

The present invention provides an electric compressor for a vehicle airconditioner, wherein a case is formed by injecting a molten metal into amold, and a compression unit for compressing a refrigerant isaccommodated inside, and wherein a machined portion is formed on onlyone of an inner circumferential surface in contact with the refrigerantand an outer circumferential surface adjacent to the innercircumferential surface.

According to the present invention, it is possible to prevent themachined portion formed at the inner circumferential surface side of thecase and the machined portion formed at the outer circumferentialsurface side from becoming adjacent, thus preventing the refrigerantfrom leaking from the inside to the outside of the case.

Specifically, because the inner circumferential surface or the outercircumferential surface adjacent to the machined portion is notprocessed, it is possible to leave a casting surface including a chilllayer that has fewer cavities, such as shrinkage cavities, on the innercircumferential surface or the outer circumferential surface. Therefore,it is possible to reduce the probability of the above-described cavitiespassing through from the inside to the outside of the case, thusreducing the incidence of refrigerant leaks.

In the invention described above, a thickness between the machinedportion and an inner circumferential portion, or a thickness between themachined portion and an outer circumferential portion is preferablylarger than that between the inner circumferential surface and the outercircumferential surface.

In this way, it is possible to ensure sufficient thickness between themachined portion and the inner circumferential portion or between themachined portion and the outer circumferential portion in the case, thuspreventing refrigerant leaks.

In other words, by ensuring sufficient thickness of the case, it ispossible to reduce the probability of the above-described cavitiespassing through from the inside to the outside of the case, thusreducing the incidence of refrigerant leaks.

In the invention described above, a pressure case that accommodates thecompression unit and an electrical-equipment case that accommodateselectrical parts that control an electric motor for driving thecompression unit are preferably integrally provided in the case, and themolten metal is preferably injected from the pressure case side.

In this way, by injecting the molten metal from the pressure case sideto form the case, it is possible to reduce the incidence of cavities inthe pressure case. Accordingly, it is possible to reduce the probabilityof the above-described cavities passing through from the inside to theoutside of the pressure case, thus reducing the incidence of refrigerantleaks.

In the configuration described above, it is preferable that the pressurecase be a substantially cylindrical member having at least a bottomsurface, a plurality of ribs that radially extend being provided on thebottom surface, and a suction hole through which the refrigerant flowsinto the pressure case from outside be provided so as to pass throughbetween the plurality of ribs in the case.

In this way, it is possible to prevent interference between the suctionhole and the ribs, thus ensuring the strength of the pressure case. Morespecifically, because the ribs do not block the flow of the refrigerantflowing inside through the suction hole, the shape of the ribs is notrestricted. Therefore, the ribs can be formed in any shape required toensure the strength of the pressure case, thus ensuring the strength ofthe pressure case.

In addition, to avoid interference between the suction hole and theribs, compared with a case in which the positions of the suction holeand the ribs are shifted relative to each other in the center axisdirection of the pressure case, it is possible to reduce the size of thepressure case in the center axis direction.

In the configuration described above, it is preferable that the pressurecase be a substantially cylindrical member having at least a bottomsurface, a plurality of ribs that radially extend be provided on thebottom surface, a suction hole through which the refrigerant flows intothe pressure case from outside be provided so as to pass through betweenthe plurality of ribs in the case, a boss that supports a rotation shaftof the compression unit be provided at the center portion of the bottomsurface, and the suction hole be a through-hole extending toward theboss.

In this way, when the refrigerant flowing into the pressure case throughthe suction hole includes lubricant, such as lubricating oil, thelubricant flows toward the boss together with the refrigerant and issupplied between the rotation shaft and the boss. Accordingly,lubrication between the rotation shaft and the boss can be ensured.

In the configuration described above, it is preferable that the pressurecase be a substantially cylindrical member having at least a bottomsurface, a plurality of ribs that radially extend be provided on thebottom surface, a suction hole through which the refrigerant flows intothe pressure case from outside be provided so as to pass through betweenthe plurality of ribs in the case, a discharge hole in which therefrigerant flows out from the pressure case be provided in the pressurecase, and the suction hole and the discharge hole be formedsubstantially in the same direction with respect to the case.

In this way, compared with a case in which the suction hole and thedischarge hole are formed in different directions, because bothdirections are substantially the same, it is possible to reduce the sizein the width direction of the pressure case, i.e., the size in adirection orthogonal to the center axis.

In the configuration described above, it is preferable that the pressurecase be a substantially cylindrical member having at least a bottomsurface, a plurality of ribs that radially extend be provided on thebottom surface, a suction hole through which the refrigerant flows intothe pressure case from outside be provided so as to pass through betweenthe plurality of ribs in the case, and the suction hole be located at aposition higher than the central axis of the pressure case when thepressure case is attached to a desired attachment position.

In this way, when attaching the pressure case to a desired attachmentposition, the lubricant retained in the pressure case can be preventedfrom flowing out from the suction hole.

The electric compressor for the vehicle air conditioner according to thepresent invention provides advantages in that it is possible to preventa machined portion formed at an inner circumferential surface side and amachined portion formed at an outer circumferential surface side in acase from becoming adjacent, as well as to prevent refrigerant fromleaking from the inside to the outside of the case.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view for explaining, in outline, the configurationof an electric compressor according to an embodiment of the presentinvention.

FIG. 2 is a perspective view for explaining the configuration of a motorcase in FIG. 1.

FIG. 3 is a diagram of a box, viewed from an opening side, forexplaining the configuration of the motor case in FIG. 2.

FIG. 4 is a diagram of a cylindrical portion, viewed from an openingside, for explaining the configuration of the motor case in FIG. 2.

FIG. 5 is a sectional view for explaining the configuration of a portionwhere a terminal portion is attached in the motor case in FIG. 1.

FIG. 6 is a sectional view for explaining the configuration of a suctionportion in the motor case in FIG. 3.

EXPLANATION OF REFERENCE SIGNS

-   -   1: electric compressor (electric compressor for vehicle air        conditioner)    -   3: scroll compression unit (compression unit)    -   11: main shaft (rotation shaft)    -   13: housing (case, pressure case)    -   15: upper bearing case (case, pressure case)    -   67: motor case (case, pressure case)    -   69: inverter unit (electrical part)    -   77: cylindrical portion (case, pressure case)    -   77A: inner circumferential surface    -   83: box (electrical-equipment case)    -   101: screw hole (machined portion)    -   113: securing bolt hole (machined portion)    -   91: sub-boss (boss)    -   93: rib    -   122: suction hole    -   123: mounting bolt hole (machined portion)

BEST MODE FOR CARRYING OUT THE INVENTION

An electric compressor according to an embodiment of the presentinvention will be described with reference to FIGS. 1 to 6.

FIG. 1 is a sectional view for explaining, in outline, the configurationof an electric compressor according to an embodiment of the presentinvention.

In this embodiment, a description will be given where an electriccompressor (electric compressor for a vehicle air conditioner) 1 isapplied to the electric compressor that is used for a vehicle airconditioner and whose rotational speed for driving thereof is controlledby an inverter.

As shown in FIG. 1, the electric compressor 1 is provided with a scrollcompression unit (compression unit) 3 that compresses a refrigerant usedfor a vehicle air conditioner, and a motor unit 5 that drives the scrollcompression unit 3.

The scroll compression unit 3 is provided with a fixed scroll (notshown) and an orbiting scroll (not shown) that compress the refrigerant,a main shaft (rotation shaft) 11 that transmits a rotational drivingforce of the motor unit 5 to the orbiting scroll, a housing (case,pressure case) 13 that accommodates the fixed scroll and the orbitingscroll therein, and an upper bearing case (case, pressure case) 15,described below, that supports the main shaft 11.

The main shaft 11 is a cylindrical member extending from the motor unit5 toward the scroll compression unit 3 and transmits the generatedrotational driving force by the scroll compression unit 3 to theorbiting scroll to orbitally drive the orbiting scroll.

The motor unit 5 is provided with a stator 63 and a rotor 65 that drivethe main shaft 11, a motor case (case, pressure case) 67 thataccommodates the stator 63 and the rotor 65, and an inverter unit(electrical part) 69 that controls an AC current supplied to the stator63.

FIG. 2 is a perspective view for explaining the configuration of themotor case in FIG. 1.

As shown in FIG. 2, the motor case 67 is provided with a cylindricalportion (case, pressure case) 77, with a cylindrical shape, thataccommodates the stator 63 and the rotor 65, and a box(electrical-equipment case) 83 that accommodates the inverter unit 69.

FIG. 3 is a diagram of the box, viewed from an opening side, forexplaining the configuration of the motor case in FIG. 2. FIG. 4 is adiagram of the cylindrical portion, viewed from an opening side, forexplaining the configuration of the motor case in FIG. 2.

As shown in FIG. 3, a plurality of screw holes (machined portions) 101used for securing the inverter unit 69 are formed in the box 83.

As shown in FIG. 3, the screw holes 101 are formed at edges of the box83. As shown in FIG. 4, thick portions 102 that have machining allowancefor the screw holes 101 and that have a thickness (plate thickness)substantially the same as that of other portions are formed on a surfaceof the box 83 facing the cylindrical portion 77. The thick portions 102have casting surfaces that are not processed.

FIG. 5 is a sectional view for explaining the configuration of a portionwhere a terminal portion is attached in the motor case in FIG. 1.

As shown in FIGS. 1 and 5, an opening 111 for connecting the inverterunit 69 and the motor unit 5 is provided in the cylindrical portion 77,and securing bolt holes (machined portions) 113 are formed. Securingbolts for securing a terminal portion 112 that covers the opening 111are screwed into the securing bolt holes 113.

The securing bolt holes 113 are holes that extend from the box 83 towardthe cylindrical portion 77 and formed in the box 83.

Protrusions 114 that have machining allowance for the securing boltholes 113 and have a thickness (plate thickness) substantially the sameas that of other portions are formed at positions corresponding to thesecuring bolt holes 113 on an inner circumferential surface 77A of thecylindrical portion 77. The protrusions 114 have casting surfaces thatare not processed.

By doing so, with the protrusions 114, it is possible to absorb thedepth of a screw required for forming the securing bolt holes 113.Accordingly, the terminal portion 112 can be disposed close to thecylindrical portion 77, thus reducing the size of the electriccompressor 1.

FIG. 6 is a sectional view for explaining the configuration of a suctionportion in the motor case in FIG. 3.

A bottom surface 79 is provided at one end of the cylindrical portion77, and a suction portion 121 is provided close to the bottom surface79, as shown in FIGS. 4 and 6.

As shown in FIG. 4, a cylindrical sub-boss (boss) 91 that supports anend of the main shaft 11 is provided at the center portion of the bottomsurface 79, and six ribs 93 outwardly extend from the sub-boss 91 in theradial direction at equal intervals.

The suction portion 121 is a portion to which an external refrigerantpipe is connected and through which the refrigerant flows into thecylindrical portion 77.

As shown in FIG. 4, in the state where the electric compressor 1 isattached to a desired attachment position, the suction portion 121 isdisposed higher than the center axis of the electric compressor 1 or thecenter axis of the main shaft 11.

By doing so, when attaching the electric compressor 1 to a desiredattachment position, lubricating oil retained in the cylindrical portion77 can be prevented from flowing out from the suction hole 122.

As shown in FIG. 6, the suction portion 121 is provided with a suctionhole 122 through which the refrigerant flows and a mounting bolt hole(machined portion) 123 used for securing the external refrigerant pipe.

The suction hole 122 is a through-hole that connects the inside andoutside of the cylindrical portion 77 and is a channel through which therefrigerant flows inside the cylindrical portion 77 from outside.

As shown in FIG. 4, the suction hole 122 is formed so as to open betweenthe ribs 93 and to extend toward a sub-boss 91. In addition, the suctionhole 122 is formed so as to extend substantially parallel with adischarge hole of a discharge portion (not shown).

The mounting bolt hole 123 is a hole into which a bolt used for securingthe external refrigerant pipe is screwed. As shown in FIG. 6, themounting bolt hole 123 is a hole that extends from the outside to theinside of the cylindrical portion 77 and is substantially parallel withthe suction hole 122.

A thick portion 124 that has machining allowance for the mounting bolthole 123 and has a thickness (plate thickness) substantially the same asthat of other portions is formed on the inner circumferential surface77A at a position corresponding to the mounting bolt hole 123 in thecylindrical portion 77. The thick portion 124 has a casting surface thatis not processed.

The motor case 67 is formed by, for example, die-casting, i.e.,injecting a molten aluminum alloy into a metal mold. An inlet (spruegate) for the molten aluminum alloy is preferably disposed on the bottomsurface 79.

By doing so, cavities are less likely to be formed in the cylindricalportion 77 constituting a pressure vessel.

Next, compression of the refrigerant at the electric compressor 1 ofthis embodiment will be described.

As shown in FIG. 1, a DC current is supplied from outside of theinverter, is frequency controlled by an electronic device at theinverter unit 69, and is supplied to the motor unit 5.

In the motor unit 5, a stator 63 produces an AC magnetic field based onan AC current that is frequency controlled. The rotor 65 generates arotational driving force due to interaction with the produced ACmagnetic field. The rotational driving force generated by the rotor 65is transmitted to the main shaft 11.

The rotational driving force is transmitted to the orbiting scroll atthe scroll compression unit 3 via the main shaft 11. The orbiting scrollis driven so as to revolve while restricting its movement with arotation-preventing portion (not shown).

When the orbiting scroll is driven to revolve, a compression chamberformed between it and the fixed scroll compresses the refrigerant, whosevolume is reduced as it moves from an outer circumferential end towardthe center.

The refrigerant compressed in the compression chamber is discharged intoa discharge chamber through a discharge hole of the fixed scroll anddischarged outside the housing from the discharge chamber.

With the above-described configuration, it is possible to prevent amachined surface or the like at the inner circumferential surface sidefrom becoming adjacent to, for example, the screw holes 101 formed atthe outer circumferential surface side in the cylindrical portion 77,thus preventing the refrigerant from leaking from the inside to theoutside of the cylindrical portion 77 or the like.

Specifically, because the thick portions 102 that are not machined areprovided on the inner circumferential surface adjacent to, for example,the screw holes 101, it is possible to leave a casting surface includinga chill layer or the like that has fewer cavities, such as shrinkagecavities, on the inner circumferential surface. Therefore, it ispossible to reduce the probability of the above-described cavitiespassing through from the inside to the outside of, for example, thecylindrical portion 77, thus reducing the incidence of refrigerantleaks.

By providing the thick portions 102 or the like, it is possible toensure sufficient thickness between, for example, the screw holes 101and an inner circumferential portion in the cylindrical portion 77, thuspreventing refrigerant leaks.

In other words, by ensuring sufficient thickness of the cylindricalportion 77, it is possible to reduce the probability of theabove-described cavities passing through from the inside to the outsideof the cylindrical portion 77, thus reducing the incidence ofrefrigerant leaks.

By injecting the molten metal from the cylindrical portion 77 to formthe motor case 67 or the like, it is possible to reduce the incidence ofcavities in the cylindrical portion 77. Accordingly, it is possible toreduce the probability of the above-described cavities passing throughfrom the inside to the outside of the cylindrical portion 77, thusreducing the incidence of refrigerant leaks.

Because the suction hole 122 is formed between the ribs 93, it ispossible to prevent interference between the suction hole 122 and theribs 93, thus ensuring the strength of the cylindrical portion 77. Morespecifically, because the ribs 93 do not block the flow of therefrigerant flowing inside through the suction hole 122, the shape ofthe ribs 93 is not restricted. Therefore, the ribs 93 can be formed inany shape required to ensure the strength of the cylindrical portion 77,thus ensuring the strength of the cylindrical portion 77.

In addition, to avoid interference between the suction hole 122 and theribs 93, compared with a case in which the positions of the suction hole122 and the ribs 93 are shifted in the center axis direction of thecylindrical portion 77, it is possible to reduce the size of thecylindrical portion 77 in the center axis direction.

Because the suction hole 122 is formed so as to extend toward thesub-boss 91, the lubricating oil contained in the refrigerant flowinginto the cylindrical portion 77 by passing through the suction hole 122flows toward the sub-boss 91 together with the refrigerant and issupplied between the main shaft 11 and the sub-boss 91. Accordingly,lubrication between the main shaft 11 and the sub-boss 91 can beensured.

Compared with a case in which the suction hole 122 and the dischargehole are formed in different directions, because the suction hole 122and the discharge hole are formed substantially in the same direction,it is possible to reduce the size in the width direction of thecylindrical portion 77, i.e., the size in a direction orthogonal to thecenter axis of the electric compressor 1.

In addition, in the above-described embodiment, a description is givenof an example in which the machined portions, such as the screw holes101, are formed on the outer circumferential of, for example, thecylindrical portion 77, and the casting surface is left on the innercircumferential surface 77A. However, it is not limited thereto; thecasting surface may be left on the outer circumferential surface of, forexample, the cylindrical portion 77, and the machined portions may beformed on the inner circumference.

1. An electric compressor for a vehicle air conditioner, wherein a caseis formed by injecting a molten metal into a mold, and a compressionunit for compressing a refrigerant is accommodated inside, and wherein amachined portion is formed on one of an inner circumferential surface incontact with the refrigerant and an outer circumferential surfaceadjacent to the inner circumferential surface.
 2. An electric compressorfor a vehicle air conditioner according to claim 1, wherein a thicknessbetween the machined portion and an inner circumferential portion, or athickness between the machined portion and an outer circumferentialportion is larger than that between the inner circumferential surfaceand the outer circumferential surface.
 3. An electric compressor for avehicle air conditioner according to claim 1, wherein a pressure casethat accommodates the compression unit and an electrical-equipment casethat accommodates electrical parts that control an electric motor fordriving the compression unit are integrally provided in the case, andthe molten metal is injected from the pressure case side.
 4. An electriccompressor for a vehicle air conditioner according to claim 3, whereinthe pressure case is a substantially cylindrical member having at leasta bottom surface, a plurality of ribs that radially extend beingprovided on the bottom surface, and a suction hole through which therefrigerant flows into the pressure case from outside is provided so asto pass through between the plurality of ribs in the case.
 5. Anelectric compressor for a vehicle air conditioner according to claim 4,wherein a boss that supports a rotation shaft of the compression unit isprovided at the center portion of the bottom surface, and the suctionhole is a through-hole extending toward the boss.
 6. An electriccompressor for a vehicle air conditioner according to claim 4, wherein adischarge hole in which the refrigerant flows out from the pressure caseis provided in the pressure case, and the suction hole and the dischargehole are formed substantially in the same direction with respect to thecase.
 7. An electric compressor for a vehicle air conditioner accordingto claim 4, wherein the suction hole is located at a position higherthan the central axis of the pressure case when the pressure case isattached to a desired attachment position.